The present invention relates generally to battery packs, battery operated devices, and methods for their use. The invention may find particular use in slide type battery packs having a plurality of cells. In particular, the present invention relates to mechanisms for ejecting detachable battery packs from battery operated devices.
Electrical power tools, such as drills, screwdrivers, saws, etc., are in widespread use. While these tools can be powered by an AC power source using an electrical cord, battery operated tools offer their operators greater mobility. Battery operated tools also eliminate the need for extension cords, which can be quite cumbersome. However, battery operated devices also have limitations. The batteries can hold a limited amount of electrical power. To alleviate this problem, power tool manufacturers developed more powerful packs. As a result, battery packs have become large and heavy. This increase in weight has led manufacturers of battery operated power tools to develop locking mechanisms that secure these large, heavy battery packs in electrical contact with the power tool. Unfortunately, the larger and heavier the battery pack, the stronger the locking mechanism. To change the battery pack for recharging, the operator must first disable the locking mechanism and then separate the battery pack from the power tool. Because the pack is large and heavy, there is a need to assist a power tool user in separating the battery pack from the power tool.
U.S. Pat. No. 6,412,572 shows a battery ejection mechanism where a spring is used to apply a force to either the battery packer to assist a user separating the two. This approach has limitations. First, the user must compress the spring when connecting the battery. The user must apply a sufficient force to compress the spring enough for the spring to apply a large enough force to provide real assistance in the removal of these large, heavy battery packs. Thus, the effort saved by providing assistance with the removal of the battery is negated by the effort required to compress the spring when attaching the battery to the tool. Further, the spring applies a force against the battery as the operator attempts to attach the battery. This force acts to directly oppose the efforts of the operator. The battery ejection mechanism of the present invention addresses these and other problems of the art.